1. Field of the Invention
The present invention relates to infrared transmitting optical fiber materials, to a method of producing an optical fiber and to an optical fiber amplifier.
2. Description of the Related Art
The development of silica glass single-mode optical fibers has led to the possibility of broad-band communication at second and third transmission windows situated at 1.3 .mu.m and 1.5 .mu.m respectively. In 1985, an erbium-doped silica optical fiber amplifier, known as EDFA, was developed for the third transmission window, with almost 97% quantum efficiency and a large signal gain of 50 dB. The 1.5 .mu.m optical fiber amplifiers are planned for use in the transoceanic submarine cable networks. EDFA will play a key role in the high-speed data transmission networks.
However, globally the terrestrial networks utilize 1.3 .mu.m window and currently electronic repeaters are used at the signal wavelength. The electronic repeaters, used in the networks, are prohibitively high cost items. Also, the electronic repeaters inherently introduce incompatibility between optical and electronic components at high bit rate transmission (&gt;2.5 Gbit/sec). Hence there is a need for providing distortion-free amplification without converting the optical signals into an array of electrical pulses and vice-a-versa. Optical fiber amplifiers operating at 1300 nm window for passive optical networks (PONs) are therefore required.